The invention relates to an illumination device for photographic color printing, for example, enlargement or printing apparatus having color filters which can be inserted by variable amounts into the copying beam.
An illumination system of this kind is described in German Patent Specification No. 871,554, in which system the light emerging from a light source is concentrated by a condenser system and passes through an arrangement consisting of a rectangular aperture having a sliding diaphragm and three filters of maximum density each of a primary color. The sliding diaphragm consists of one or two slides, the direction of movement of which is perpendicular to the direction of movement of the filters. By suitable adjustment of the slides it is possible to obtain a continuously adjustable alteration of the brightness at the outlet of the illuminating device, without unduly altering the color balance of the copying beam. Some amount of undesirable shifting does, however, occur.